1. Field of the Invention
The present invention relates to a block and bleed valve with a magnetic coupled switch for a pneumatic operated liquid level switch for tanks and vessels.
2. Description of the Related Art
There are a number of existing devices that include float operated valves. In each case, when the liquid level rises or falls in a tank or vessel, a float shifts a pneumatic valve to one of two positions. Some existing devices couple the float to the pneumatic valve using a magnet couple while others use mechanical linkage.
Some existing devices use a block and bleed valve that is mechanically coupled to the float. The mechanical linkage complicates the use of a snap switch. The mechanical linkage requires a seal between the float and the switch.
Based on the foregoing, it is desirable to provide a float operated pneumatic valve utilizing a magnetically coupled block and bleed valve instead of a mechanically coupled block and bleed valve. This makes the use of a simple and reliable magnetically operated snap acting switch possible. The snap acting switch actuates the block and bleed valve. Since the snap acting switch is magnetically coupled to the float, no seals between the float compartment and the switch compartment are needed.
Some existing pneumatic conical or tapered valves with a magnetic switch are direct acting, such as seen in Felgote (U.S. Pat. No. 2,893,427). It is desirable to provide a magnetic opposing pole snap switch with a block and bleed valve arrangement.
It would also be desirable to provide a block and bleed valve on a float operated pneumatic valve assembly wherein a block and bleed valve is externally adjustable.